1. Field of the Invention
The invention relates generally to an improvement of a woven fabric product such as a sleeping bag, clothes, or a sleeping bag cover.
2. Description of Related Art
Conventionally, a sleeping bag is an example of a woven fabric product. For example, there is a sleeping bag including: a heat insulating means for defining a long inside space for placing a user's body and keeping the inside space warm; an opening to the inside space, that is made in the heat insulating means; and elastic elements for compressing the heat insulating means in a direction to reduce the cross-sectional area of the inside space; wherein the elastic elements are located at specified intervals along the entire length of the heat insulating means (see, for example, Japanese Utility Model Registration No. 2079863).
There is another type of sleeping bag including: a sleeping bag main body that has an inside woven fabric, an outside woven fabric, and a heat insulating material filled in the space between the inside woven fabric and the outside woven fabric, and that forms a long inside space for placing a user's body, and keeps the inside space warmer than the outside air; and an opening to the inside space that is made in the sleeping bag main body; wherein the sleeping bag main body has the inside woven fabric and the outside woven fabric which are wider than a specified width that fits the constitution of the user's body and which can be contracted to the specified width, when the sleeping bag is not in use, by means of elastic elements placed at appropriate positions; and wherein the sleeping bag main body is configured so that it can expand from the specified width to the wider width, or contract from the wider width to the specified width (see, for example, Japanese Patent Laid-Open (Kokai) Application Publication No. 2001-46205).
Each of the conventional sleeping bags described above is gathered in its widthwise direction so that the sleeping bag will fit the user's body adequately when they wear it, and the sleeping bag can stretch or contract in its widthwise direction in accordance with the user's movement of, for example, turning over in their sleep, or changing their clothes or sitting cross-legged inside the sleeping bag. Therefore, a large amount of cloth (woven fabric) is needed to make the sleeping bag, so the weight and volume of the sleeping bag increase, which is inconvenient in terms of portability and storage.